Ruthenium carbonyls reactions

Grignard additions, 9, 59, 9, 64 indium-mediated allylation, 9, 687 in nickel complexes, 8, 150 ruthenium carbonyl reactions, 7, 142 ruthenium half-sandwiches, 6, 478 and selenium electrophiles, 9, W11 4( > 2 in vanadocene reactions, 5, 39 Nitrites, with trinuclear Os clusters, 6, 733 Nitroalkenes, Grignard additions, 9, 59-60 Nitroarenes, and Grignard reactivity, 9, 70 Nitrobenzenes, reductive aminocarbonylation, 11, 543... 

Reactive Intermediates in the Thermal and Photochemical Reactions of IHnuclear Ruthenium Carbonyl Clusters... 

The dominant role of copper catalysts has been challenged by the introduction of powerful group VIII metal catalysts. From a systematic screening, palladium(II) and rhodium(II) derivatives, especially the respective carboxylates62)63)64-, have emerged as catalysts of choice. In addition, rhodium and ruthenium carbonyl clusters, Rh COJjg 65> and Ru3(CO)12 e6), seem to work well. Tables 3 and 4 present a comparison of the efficiency of different catalysts in cyclopropanation reactions with ethyl diazoacetate under standardized conditions. 

The Water Gas Shift Reaction as Catalyzed by Ruthenium Carbonyl in Acidic Solutions... 

Although related reactions have also been done under low pressures/ very low rates of product formation are observed (8/10/11). We have found/ however, that a ruthenium carbonyl catalyst is quite active for converting H2/CO to methanol under moderate pressures (below 340 atm). More significantly, we also discovered that an ethylene glycol product could be obtained from this catalyst by use of carboxylic acid promoters or solvents (12) This remarkable and intriguing promoter effect deserved, we felt, further mechanistic investigation... 

The reactions with ruthenium carbonyl catalysts were carried out in pressurized stainless steel reactors glass liners had little effect on the activity. When trimethylamine is used as base, Ru3(CO) 2> H Ru4(CO) 2 an< H2Ru4(CO)i3 lead to nearly identical activities if the rate is normalized to the solution concentration of ruthenium. These results suggest that the same active species is formed under operating conditions from each of these catalyst precursors. The ambient pressure infrared spectrum of a typical catalyst solution (prepared from Ru3(CO)i2> trimethylamine, water, and tetrahydrofuran and sampled from the reactor) is relatively simple (vq q 2080(w), 2020(s), 1997(s), 1965(sh) and 1958(m) cm ). However, the spectrum depends on the concentration of ruthenium in solution. The use of Na2C(>3 as base leads to comparable spectra. 

Although this spectrum does not correspond to any particular ruthenium carbonyl complex, it is consistent with the presence of one or more anionic ruthenium carbonyl complexes, perhaps along with neutral species. Work is in progress with a variable path-length, high pressure infrared cell designed by Prof. A. King, to provide better characterization of species actually present under reaction conditions. 

Effect of Solvent and Base on the Ruthenium Carbonyl/Tri-methylamine System. Solvent plays an important role in the rate of hydrogen production. The ideal solvents are tetrahydrofuran, diglyme, and dimethoxyethane. Alcohols are only slightly less effective. Apparently the solvent must be miscible with water, promote ion formation, and be capable of weakly coordinating with the coordinately unsaturated species formed in the course of the reaction. 

Effect of Base on the Ruthenium Carbonyl-Catalyzed Water Gas Shift Reaction... 

Table 2 Effect of the type of base on the ruthenium carbonyl catalyzed water gas shift reaction. Conditions 0.05 mmol Ru3(CO)12, 92 mmol 1-butene, base and water diluted to 100 ml with diglyme, 750 psi ( 52 atm) CO, 100 °C, 10 hours, 0.31 L reactor58 ... 

However, while ruthenium carbonyl was found to decompose the formate ion in basic media, the rate was slower (<0.1 mmol trimethyl ammonium formate to H2 and C02 per hour) than the rate of the water-gas shift reaction (>0.4 mmol H2/hr) at 5 atm CO and 100 °C. Increasing CO pressure decreased the formate decomposition rate. However, it was observed that increasing the CO pressure from 5 atm CO to 50 atm increased the H2 production rate to 10 mmol/hr. They proposed, in a similar manner to Pettit et al.,34 a mechanism that involved nucleophilic attack by amine (instead of hydroxide). Activation of the metal carbonyl (e.g., Ru3(CO) 2 cluster to Ru(CO)5) was suggested to be favored by dilution, increases in CO pressure, or, in the case of Group VIb metal carbonyl complexes, photolytic promotion. The mechanism is shown below in Scheme 9 ... 

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